From be33d3a5156ea3fde221c9e174ad0405eb8d1f8d Mon Sep 17 00:00:00 2001 From: Dean Camera Date: Mon, 18 Mar 2013 17:18:11 +0000 Subject: Update Mass Storage bootloader so that it can support devices with only 4KB bootloader sections by creating a special AUX section before the real bootloader section to store part of the bootloader code. --- Bootloaders/MassStorage/BootloaderMassStorage.txt | 36 ++++++++++++++++++----- 1 file changed, 29 insertions(+), 7 deletions(-) (limited to 'Bootloaders/MassStorage/BootloaderMassStorage.txt') diff --git a/Bootloaders/MassStorage/BootloaderMassStorage.txt b/Bootloaders/MassStorage/BootloaderMassStorage.txt index 7ca7c1f85..19751d3be 100644 --- a/Bootloaders/MassStorage/BootloaderMassStorage.txt +++ b/Bootloaders/MassStorage/BootloaderMassStorage.txt @@ -12,6 +12,8 @@ * * \li Series 7 USB AVRs (AT90USBxxx7) * \li Series 6 USB AVRs (AT90USBxxx6) + * \li Series 4 USB AVRs (ATMEGAxxU4) - See \ref SSec_Aux_Space + * \li Series 2 USB AVRs (AT90USBxx2, ATMEGAxxU2) - See \ref SSec_Aux_Space * * \section Sec_Info USB Information: * @@ -49,7 +51,7 @@ * firmware image file, to load firmware onto the AVR. * * Out of the box this bootloader builds for the AT90USB1287 with an 8KB bootloader section size, and will fit - * into 8KB of bootloader space. If you wish to alter this size and/or change the AVR model, you will need to + * into 6KB of bootloader space. If you wish to alter this size and/or change the AVR model, you will need to * edit the MCU, FLASH_SIZE_KB and BOOT_SECTION_SIZE_KB values in the accompanying makefile. * * When the bootloader is running, the board's LED(s) will flash at regular intervals to distinguish the @@ -100,6 +102,22 @@ * #define BOOTLOADER_ADDRESS_LENGTH 4 * \endcode * + * From the application the API support of the bootloader can be detected by reading the FLASH memory bytes located at address + * \c BOOTLOADER_MAGIC_SIGNATURE_START and comparing them to the value \c BOOTLOADER_MAGIC_SIGNATURE. The class of bootloader + * can be determined by reading the FLASH memory bytes located at address \c BOOTLOADER_CLASS_SIGNATURE_START and comparing them + * to the value \c BOOTLOADER_MASS_STORAGE_SIGNATURE. The start address of the bootloader can be retrieved by reading the bytes + * of FLASH memory starting from address \c BOOTLOADER_ADDRESS_START. + * + * \subsection SSec_Aux_Space Auxiliary Bootloader Section + * To make the bootloader function on smaller devices (those with a physical bootloader section of smaller than 6KB) a second + * section of memory (called the Auxiliary Bootloader Section) is added before the start of the real bootloader section, + * and is filled with a portion of the bootloader code. This allows smaller devices to run the bootloader, at the cost of an + * additional portion of the device's FLASH (the bootloader section size in KB subtracted from the 6KB total size). A small + * trampoline is inserted at the start of the auxiliary section so that the bootloader will run normally in the case of a blank + * application section. + * + * On devices supporting a 8KB bootloader section size, the AUX section is not created in the final binary. + * * \subsection SSec_API_MemLayout Device Memory Map * The following illustration indicates the final memory map of the device when loaded with the bootloader. * @@ -121,6 +139,16 @@ * | | * | | * | | + * | | + * +----------------------------+ FLASHEND - BOOT_SECTION_SIZE - BOOT_AUX_SECTION_SIZE + * | Booloader Start Trampoline | + * | (Not User App. Accessible) | + * +----------------------------+ FLASHEND - BOOT_SECTION_SIZE - BOOT_AUX_SECTION_SIZE + 4 + * | | + * | Auxiliary Bootloader | + * | Space for Smaller Devices | + * | (Not User App. Accessible) | + * | | * +----------------------------+ FLASHEND - BOOT_SECTION_SIZE * | | * | Bootloader Application | @@ -138,12 +166,6 @@ * +----------------------------+ FLASHEND * \endverbatim * - * Bootloaders reporting a device release revision number of 1.00 or greater are bootloader API enabled. From the application - * the API support of the bootloader can be detected by reading the FLASH memory bytes located at address \c BOOTLOADER_MAGIC_SIGNATURE_START - * and comparing them to the value \c BOOTLOADER_MAGIC_SIGNATURE. The class of bootloader can be determined by reading the - * FLASH memory bytes located at address \c BOOTLOADER_CLASS_SIGNATURE_START and comparing them to the value \c BOOTLOADER_MASS_STORAGE_SIGNATURE. - * The start address of the bootloader can be retrieved by reading the bytes of FLASH memory starting from address \c BOOTLOADER_ADDRESS_START. - * * \section Sec_Options Project Options * * The following defines can be found in this demo, which can control the demo behaviour when defined, or changed in value. -- cgit v1.2.3